This invention relates to a new and improved header assembly for plate-type evaporative heat exchangers.
Many state-of-the-art, plate-type, evaporative heat exchangers incorporate very thin aluminum sheets as the plate material. These plates are attached alternately along opposite edges to form a cross-flow heat exchanger. Most of these heat exchangers have a wicking material or a wettable material laminated to one surface of the plate. These material surfaces of the plates define the evaporative cooling channels. Although the thinness of the aluminum plates provides improved heat exchange, the pliability of these thin plates often results in uneven spacing of the openings into the evaporative cooling channels between the edges of the attached plates. Therefore, during operation, more water is distributed onto some of the evaporative cooling surfaces than others, while simulataneously, more secondary air is blown through some of the evaporative cooling channels than others. This uneven distribution of water and air entering into the evaporative cooling channels results in diminished heat exchange.
Typically, sprinkler heads are used to supply water onto the evaporative cooling surfaces of the state-of-the-art heat exchangers. Sprinkler heads for evaporative heat exchangers are undesirable for several reasons. First, the water spray humidifies the secondary air before it enters into the evaporative cooling channels. Humidified secondary air is counterproductive for evaporative cooling purposes. Second, due to the spray pattern of the water over the heat exchanger, sprinkler heads inherently cannot uniformly distribute water onto the evaporative cooling surfaces. In addition to the spray pattern, the number and arrangement of the sprinkler heads further complicate uniform water distribution. Third, the sprinkler heads spray water from small orifices that might clog with impurities or debris which might accumulate during the recirculation of the unevaporated water. Fourth, spraying water from small orifices requires relatively high pump horsepower to overcome the pressure loss incurred at the orifices of the sprinkler heads.
It is from these considerations and others that the present invention evolved.